The present invention relates to an apparatus for mounting on a frame an electrical appliance such as electromagnetic contactor which opens and closes an input power line for an electric motor and in particular to an apparatus for mounting on a frame an electrical appliance in which a slidable member which is fitted in a guide recess formed on an attachment surface of the appliance is biased by the biasing force of a biasing spring for securing the frame on the attachment surface of the appliance.
A prior art electromagnetic contactor is often used in such a manner that it is mounted on a frame at a predetermined elevation in a house. An example of a conventional electromagnetic contactor is illustrated in FIGS. 1 to 3.
FIG. 1 is a bottom view showing a conventional electromagnetic contactor. FIG. 2 is a sectional view taken along the line II--II in FIG. 1. FIG. 3 is a schematic view showing the essential part of the contactor.
In the drawings, a main body 1 of an electromagnetic relay is provided with a mounting recess 2 for mounting on a frame 13 at the bottom thereof, which will be described hereafter. At one side of the mounting recess 2 are formed a plurality of engagement projections 3 and 3a which project in opposite inner directions. At the side of the mounting recess opposite to the engagement projections 3 and 3a are formed a guide recess 4 which is normal to the mounting recess 2. A pair of guide projections 5 and 5a which project from the opposite sides of the guide recess 4 in opposite inner directions at a position close to the side of the mounting recess 2. A projection 6 which projects in a downward direction at a mid position between the sides of recess 4 and in the vicinity of an end of the recess 4 opposite to the mounting recess 2. A slidable member 7 which is substantially T-shaped is slidably fitted into the guide recess 4 and is provided with a rectangular hole 8 at the center thereof, said hole 8 extending through the member 7. The hole 8 is provided with a spring stopper 9 at a front end side thereof. The slidable member 7 includes a stepped portion 10 which is to be engaged with the frame 3, a spring 12 disposed between the projections 6 and 9 and the channel shaped frame 13 having mounting projection 14 and 14a at the opposite sides thereof.
The mounting apparatus which comprises the parts mentioned-above is assembled as follows: The slidable member 7 is inserted into the guide recess 4 so that the projection 6 is fitted into the guide hole 8. The slidable member 7 is furthermore inserted until the front end thereof is positioned between the guide projections 5 and 5a. A coil spring 12 is disposed between the projections 6 and 9. This causes the slidable member 7 to be biased and slide in a direction designated by an arrow A by a coil spring 12 until a shoulder abuts on the outer wall of the main body of the electromagnetic contactor. At this time, the front end of the slidable member 7 is projected into the mounting recess 2 so that the engagement portion 10 is substantially aligned with the mounting recess 2.
In order to mount the electromagnetic contactor on the frame 13, the slidable member 7 is first slid in a direction of an arrow B against the force of the coil spring 12. The frame 13 is fitted into the mounting recess 2 with the engagement flanges 3 and 3a being engaged with the mounting projections 14 and 14a of the frame 13. If the slidable member 7 is released under such position, the slidable member 7 is slid in a direction of the arrow A by being biased by the coil spring 12. The engagement portion 10 of the member 7 is brought into engagement with the other mounting projection 14a of the frame 13 so that the electromagnetic contactor is firmly secured to the frame 13.
Since the length of the coil spring 12 is short in the afore-mentioned mounting apparatus, the guide length a determined by the outer side of the guide projections 5 and 5a in the guide recess 4 and the front end of the slidable member 7 and the movement length b of the slidable member 7 have a relation a&lt;b. Accordingly the slidable member 7 is readily separated from the engagement projections 5 and 5a when the slidable member 7 is slid in a direction of arrow B. If the slidable member 7 is escaped from the guide recess 4, small parts would be scattered so that it would not only take a long period of time to find them, and it is also very troublesome to assemble them since the coil spring 12 is small. In order to solve such problem, it may be proposed that the length of compressed coil spring 12 be made longer and movement length b of the slidable member 7 be made shorter so that a&gt;b. However this makes it difficult to mount the coil spring 12 and involves a high cost.